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 Whats the matter with the hole????

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Karthik

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Join date : 2009-08-09
Age : 27

PostSubject: Whats the matter with the hole????   Fri 14 Aug 2009 - 22:38

Well i would to ask a very basic question? Yeh question jab se mein electronics chalu kiya padna tab se hai
Please explain hole to me,
I have seen kinetic energy associated with holes, then tell me mass of hole?
If u say it is equal to electron then answer this please ..

say silicon atom
14 electrons, 14 protons and neutrons. so total mass is justified.
but when this atom looses electron, electron-holes pairs are generated,so now mass of atom equal to 14 electrons, 14 protons and neutrons and one hole????
Rolling Eyes Shocked cyclops
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AVBAPAT
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PostSubject: Re: Whats the matter with the hole????   Sat 15 Aug 2009 - 14:31

1. Hole is concept and not a particle.
2. u must be aware that there are electrons in conduction band. these are free electrons. They move randomly. and when under electric field they move in particular direction.
3. Movement of electrons is possible only if there is vacant state near by.
4. the electrons that are bonded to atom may also move from one atom to other atom with broken bond.
now the mobility ie ease with which electrons can move under electric field is different.
5. to understand concept of hole consider a hall with all chairs occupied except few. Now if we order people to shift to right if there is vacant seat. then at the end we will find that, all vacant chairs appear to have shifted to the left..
6. hole is absence of electrons. or unoccupied energy state in valence band.
7. to understand further u may refer to faculties-A. V. Bapat. download energy band theory lecture. password is avbapat
http://2008.ycce.edu/fac/facdocs/T2-hole-charge_density.pdf
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ravi.ranjan.rocks



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Join date : 2009-08-12

PostSubject: @ Karthik... Concept of electron holes   Sat 15 Aug 2009 - 14:59

sunny
A very niece question Karthik. Actually, electron hole is a conceptual and mathematical opposite of an electron. By this i mean that hole is an imaginary concept which is useful in study of physics, chemistry and electrical engineering. W.r.t. Si & Ge if some energy is supplied to their lattice i.e. 1.1eV in case of Si, some of electrons jump from valence band to conduction band leaving a vacancy in the valence band. This vacancy is termed as a hole. For other atoms i.e. other than semiconductor atoms are defined as cations.

In reality, due to the crystal structure properties, the hole is actually not localized to a single position. Rather, the hole is delocalized and spans an area in the crystal lattice covering many hundreds of unit cells. This is equivalent to the idea that we cannot tell which broken bond corresponds to the 'missing' electron, and is supported by uncertainty theorems from quantum mechanics.

Then in such type of dynamic system we cannot talk about exact mass of hole. It is termed as effective mass here which relates the imaginary force( force on the hole due to electric field according to coulomb's law) on the imaginary hole to the acceleration of that hole. Effective mass is also dependent on direction of movement. If effective mass is larger than electron then it has less mobility under the influence of electric field.

The holes themselves don't actually move, but a neighboring electron can move to fill the hole, leaving a hole at the place it has just come from, and in this way the holes appear to move, and the holes behave as if they were actual positively charged particles.

Material Electron effective mass Hole effective mass
Si (4.2K) 1.08 me 0.56 me
Ge 0.55 me 0.37 me
III-V
Ga,As 0.067 me 0.45 me
In,Sb 0.013 me 0.6 me
II-VI
ZnO 0.19 me 1.21 me
Zn,Se 0.17me 1.44 me
Thus we see that mass of electron and hole are not equal. Even mass of electron is not constant. All these are supported by wave nature of particle and lattice structure. If any doubt again feel free to ask..


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Karthik

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PostSubject: Thank a lot sir   Sat 15 Aug 2009 - 17:33

Thanks for that very fast response sir. I'll definitely go through the notes Idea
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